Air data probes are well known within the aerospace industry for providing information concerning the aircraft's airspeed, Mach number, and flight direction. Pitot, pitot-static, and total air temperature air data probes are exemplary, and are shown in, for example, U.S. Pat. Nos. 5,466,067 to Hagen, et al.; 5,369,993 to Hagen; 5,319,972 to Peterson, et al.; and 5,302,026 to Phillips. Air data probes are also used in industries outside of the aerospace industry, for example in weather stations and other applications where data concerning the air or atmospheric conditions are desired.
As shown in the above referenced patents, the shape of pitot and pitot-static probes include, and range from, an "L" shaped probe to a continuously swept probe. Aerodynamically compensated air data probes are shown in U.S. Pat. No. 4,730,487 to De Leo et al. The aforementioned Phillips patent shows the shape of a total air temperature probe. Other shapes are known in the industry.
Because of the environmental conditions that aircraft typically fly in, ice is known to form on the air data probes described above. When ice does form on the probe, the ability of the probe to measure air parameters deteriorates, and in some cases, the probe becomes entirely inoperable. It is therefore necessary to incorporate into the probe means to prevent the formation of ice, or to melt ice once it has formed. U.S. Pat. No. 4,730,487 to De Leo, et al. and U.S. Pat. No. 5,043,558 to Byles are illustrative of heaters used to address the formation of ice on air data probes.
One problem associated with prior art heaters shown in the aforementioned patents is that they are labor intensive to install and therefore costly to manufacture, and they are difficult to inspect. Further, if inspection indicates that the heater is not fabricated or joined to the probe in a satisfactory manner, it is difficult to perform repair operations; as a result, probes that do not meet manufacturing requirements are often scrapped.
Additionally, it is known that the prior art heaters consume relatively large amount of power from the aircraft, which is undesirable from the aircraft's point of view. This is especially the case in the construction shown in the '487 patent. In this construction, the probe includes a tubular barrel portion, and heater wires are brazed to the internal surface of the probe barrel. If ice forms on the external surface of the barrel during operation of the probe, heat must be conducted through the wall of the barrel in order to melt the ice. Because the surface of the heater wire only contacts the internal barrel surface along a tangent line, much of the heat generated by the wire never reaches the barrel wall, and is lost.
Accordingly, improvements are sought in the manufacture of air data probes, and in particular, in the construction and arrangement of heaters for preventing ice formation on air data probes.